The principal method of controlling pests, such as aphids, throughout the world is that of treating the infested crop with insecticides. However, there are drawbacks to this method such as environmental pollution, harmfulness for humans and animals, increased resistance in key pests, creation of secondary pest outbreaks, effective elimination of beneficial insects and so forth. Nowadays, there is an increasing interest in reducing the use of pesticides.
An alternative to chemical pesticides is the use of biocontrol agents such as predaceous and parasitoids for controlling insect pests. Nevertheless, millions of these beneficial insects, so-called biocontrol agents, are required for using this method in the fields. At the present time, for the mass production, it is still necessary to rear these insects on their natural hosts, for instance cereal aphids. This classical method is too expensive to allow large-scale use of beneficial insects in commercial agriculture. A solution seems to be the development of artificial media to rear these beneficial insects. Indeed, this method will allow reducing the cost of the mass production.
Since many years, the researchers develop methods to raise the beneficial insects (predators and parasitoids) on artificial media. Simmonds (1966) attempted to culture three ectoparasitic ichneumonids of coding moth pupae on nutritive gelatine slants and raw beef. Yazgan (1972) and House (1978) used a dietetic approach to prepare media utilizing existing knowledge of the nutritional requirements of insects generally, to successfully rear the parasitic hymenopteran Itoplectis conquisitor (Say) in chemically defined, synthetic diet. House (1978) encapsulated a synthetic diet within a Parafilm RTM capsule and created an artificial host that also served adequately for oviposition and rearing for I. conquisitor. Hoffman and Ignoffo (1974) and Hoffman et al., (1975) developed media that allowed at least partial success in rearing the pupal endoparasitoid, Pteromalus puparum (L.) and the egg parasitoid Trichogramma pretiosum (Riley), respectively.
Grenier et al. (1994) presented a review of over a half century of research on development of artificial media for entomophages, and report successes in producing media for ectoparasitoids and predators but not for endoparasitoids. Curiously, none of these artificial media has found its way into use in the commercial production of any entomophage, and none of these media have been incorporated into the augmentative production systems for these predators.
In order to fight against aphids, the most important pest insects in the agriculture of the temperate climatic zones, endoparasitoids are often effective biological control agents. Nevertheless, the number of parasitoids in the crops are often too low to reduce strongly the aphid populations. Thus, inundate releases of these beneficial insects are essential. Unfortunately, at the present time no artificial medium to rear these endoparasitoids was developed.
Despite considerable effort, no hymenopterous larval endoparasitoid has been successfully reared from egg to adult in artificial media. However, partial success has been attained with two braconid larval endoparasitoids, Microplitis croceipes. (Cresson) and Cardiochiles nigriceps (Viereck), and one braconid larval-pupal endoparasitoid, Diachasmimorpha longicaudata (Ashmead). Pennachio et al. (1992) have cultured the Heliothis virescens braconid larval endoparasitoid Cardiochiles nigriceps from post-germband eggs to the second instar in an artificial medium comprised of an amino acid, salt, vitamin, and carbohydrate-containing medium supplemented with bovine serum albumin, enzymatically hydrolysed lactalbumin, fetal bovine serum, egg yolk and milk. However, the larvae grew much slower than in vivo, only 10% moulted to the second instar and they did not complete development.
It is an aim of the present invention to provide methods and artificial hosts for continuous rearing endoparasitoids.
It is also an aim of the present invention to provide artificial hosts for oviposition of endoparasitoids.
It is a further aim of the invention to provide methods for producing artificial hosts for endoparasitoids.
It is also an aim of the invention to provide a means for storage of artificial hosts containing endoparasitoids and to apply them easily where they are needed for biological control programs.